Vinamidinium-based synthesis of a pyridopyrimidine-substituted zinc(II) phthalocyanine: Aggregation and antimicrobial properties

A new pyridopyrimidine-substituted zinc(II) phthalocyanine (ZnPc) was synthesized using a vinamidinium-based strategy through the preparation of a substituted phthalonitrile precursor followed by cyclotetramerization. This method provides access to phthalocyanine systems bearing heterocyclic peripheral substituents and allows further modification of ZnPc structures. The synthesized ZnPc was characterized by UV–Vis, FT–IR, and NMR spectroscopy, and its aggregation behavior was studied in different organic solvents. The compound showed solvent-dependent aggregation, suggesting that the peripheral pyridopyrimidine groups affect intermolecular interactions within the phthalocyanine system. Antimicrobial studies showed enhanced antibacterial activity under red-light irradiation compared with the unsubstituted analogue ZnPcH, together with concentration-dependent antifungal activity against Candida albicans, Candida glabrata, and Candida krusei. The results indicate that vinamidinium-derived heterocyclic substituents may be useful for the design of ZnPc derivatives with tunable aggregation behavior and antimicrobial photodynamic activity.